Absorbent pad

ABSTRACT

Absorbent pads, such as diapers, underpads and the like are made in which a hydrophilic foam sheet formed of hydrophilic polymer is contained between a facing and backing and acts as the primary absorbent in the product. The edges of the hydrophilic foam sheet are completely contained within the peripheral edges of the absorbent pad and secured against lateral extension, when wet. In the preferred structure crepe cellulose tissue is placed in contact with a surface of the hydrophilic foam sheet with the creping of the tissue, particularly where the absorbent pad is for use as a diaper, running lengthwise of the diaper.

United States Patent [72] Inventor Julius A. Lindquist Somerville, NJ.[211 App]. No. 699,096 [22] Filed Jan. 19, 1968 [45] Patented Feb. 16,1971 [73] Assignee Johnson & Johnson a corporation of New Jersey [54]ABSORBENT PAD 8 Claims, 9 Drawing Figs.

[52] U.S. Cl 128/287 [51] lnt.C1 A6lfl3/l6 [50] Field of Search 128/284,287, 290, 296

[56] References Cited UNITED STATES PATENTS 3,024,207 3/1962 Shaw et a1128/290 3,059,644 10/1962 Atkinson 128/290 3,072,123 1/1963 Davis128/284 3,295,526 l/l967 Sabee 128/287 3,431.91] 3/1969 Meisel, Jr.128/287 Primary Examiner-Charles F. Rosenbaum Attorneys-Alexander T.Kardos, Arnold S. Worfolk and Harold L. Warner ABSTRACT: Absorbent pads,such as diapers, underpads and the like are made in which a hydrophiliicfoam sheet formed of hydrophilic polymer is contained between a facingand backing and acts as the primary absorbent in the product. The edgesof the hydrophilic foam sheet are completely contained within theperipheral edges of the absorbent pad and secured against lateralextension, when wet. ln the preferred structure crepe cellulose tissueis placed in contact with a surface of the hydrophilic foam sheet withthe creping of the tissue, particularly where the absorbent pad is foruse as a diaper, running lengthwise ofthe diaper.

BRIEF DESCRIPTION OF THE INVENTION It has heretofore been the practicein the manufacture of diapers, underpads, and the like to use cellulosicfibers as the basic absorbent. Where the product was designed for asingle use, such as in the construction of disposable diapers andunderpads the absorbent was frequently formed of short length cellulosicfibers such as wood pulp and cotton linters which were generally presentin the form of cellulose wadding, where the fibers are compactedtogether in the form of relatively thin absorbent paper sheets or in theform of a relatively loose bulky fiber mass. This absorbent material isthen contained between a flexible backing and facing to form thedisposable product. I

One of the difficulties with such products is that the absorbent, wherecellulose wadding is used, tends to shred after wetting. The cellulosefibers of the absorbent tend to bunch together on wetting forming hard,uncomfortable spots in the absorbent pad. Also, where wood pulp or othershort fibers are used, unless appreciable bonding material is used, forholding the fibers together, there is a tendency for the fibers to shiftor settle, giving a nonuniform absorbent layer in the absorbent product.It has now been discovered that these problems can be alleviated andabsorbent pads having greater absorbency per given weight and of greatersoftness and resiliency when wet obtained with resulting greater comfortto a user by employing as the primary absorbent, hydrophilic foam sheetsformed of a hydrophilic polymer.

In accordance with the present invention absorbent pads I are preparedwith the primary absorbent of the pad being formed of a sheet or sheetsof hydrophilic foam in which the polymer forming the foam is itselfhydrophilic in nature. The use of hydrophilic foam sheet has manyadvantages over the use of cellulose wadding or wood pulp as the primaryabsorbent material. When wet, the hydrophilic foam sheet does not loseits resiliency but maintains its cushioning and resilientcharacteristics thus giving a comfortable absorbent product both in thedry and in the wet state. Also, for equal weight the absorbent capacityof the hydrophilic foam sheet is substantially greater than that ofcellulose waddingor wood pulp thus providing greater protection for anequal weight pad than has heretofore been obtainable with theconventional cellulose fiber absorbent fillers. Another advantage of:thehydrophilic foam sheets is that the same have substantial strength withthe result that they maintain their original sheet form with noshredding or bunching of'the absorbent in the product. Also, absorbedwater acts as a plasticizer making the hydrophilic foam sheet softer,more flexible, and conforming when wet with the result that absorbentpads using the same actually improve in physical characteristics onwetting rather than deteri orating as has been the problem with theconventional cellulosic fiber absorbents. This results in substantiallymore comfort to a user.

DETAILED DESCRIPTION OF THE PRESENT INVENTION The present invention willbe described primarily in connection witha disposable diaper. However,it willbe apparent that constructions similar to that described for thedisposable diaper can be equally well used for absorbent underpads, orother absorbent sheetlike products, the main difference being anincrease in size or other dimensions of the absorbent product. I

In practicing the present invention the primary absorbent material forthe diaper is hydrophilic foam sheet in which the hydrophilic foam isformed of a hydrophilic polymer. Hydrophilic foam sheet materials thatmay be used, for example, are cellularplastics in sheet form formed bycombining poly (oxyethylene) glycols, reaction products of ethyleneoxide with ethylene glycol, diethylene glycol and water, withdiisocyanates, for example, 2,4-Toluenediisocyanate, 2,6-Toluenediisocyanate or Toluenediisocyanate isomer mixtures.

The foaming is carried out in conventional manner. Thus, a specificexample would be where the foam for the polyurethane foam is obtainedthrough the reaction of poly (oxyethylene) diol and toluenediisocyanatein the presence of water, catalyst, and foam stabilizer in the followingproportions:

Parts y weight Poly(oxyethylene) diol, 2,000 .M.W 100Toluenediisocyanate (80/20 ratio blend of 2, 4-toluenediisoeyanate and2, 6-toluer1ediisocyanate) 38 Water 3. 1 Silicone stabilizer 1Triethylenediarnine 0. 15 Stannous octoate 0. 17

The foam sheet material used should be sufficiently flexible andresilient when in the dry state to give a resilient conformable product.This initial resiliency may be obtained with foams formed of cellulose,which are normally relatively stiff when dry, by the inclusion of aplasticizer. One of the substantial advantages of using the hydrophilicfoam sheets as the absorbent, is that the same do not lose their initialresiliency or body on wetting, as do most absorbents made out ofcellulosic fibers, but rather increase in softness and resiliencyassuring a soft cushiony feel even after absorption of substantialquantities of water. One of the primary advantages of the polyurethanehydrophilic foams is that soft resilient foam products result from thefoamed polymer alone without the necessity of including plasticizers.

Hydrophilic foam sheets formed of hydrophilic polymers, however, do havethe characteristic that when the same have absorbed substantialquantities of water they expand, increasing not only in thickness butalso in their overall dimensions. It is thus necessary that the foamsheet be restrained from lateral expansion within the absorbent padaround its edges as the hydrophilic foam will otherwise expand to thepoint where it extends substantially beyond the edges of the absorbentpad. Also many hydrophilic foam sheet materials, after they haveabsorbed appreciable amounts of water, tend to become much more limpthan when dry and unless supported tend to sag appreciably.

The hydrophilic foam sheet may be used in any desired thickness. Wherethe polymer foam has substantial softness and resiliency, the thicknessmight be limited only by the thickness and drape of the absorbent pad.However, where the polymer foam is relatively stiff, the foam sheetsshould be relatively thin to improve the flexibility of the finalproduct and preferably used together with hydrophilic foam sheets ofgreater softness to create the desired softness in the final product. Ingeneral practice, however, where using hydrophilic polyurethane foamsthe thickness of the polyurethane foam sheet will be in the rangeofabout H312 to inch.

Although foam hydrophilic sheets have substantial tensile strength evenwith thickness of only l/32 inch, they become extremely limp when wettedand have a tendency to sag badly and stretch unless supported.Accordingly, in practicing the present invention the hydrophilic foamsheet is supported by a backing sheet which has sufficient resistance todeformation and has sufficient strength to adequately support thehydrophilic foam sheet when wet and prevent its sagging.

To aid in the description of the present invention reference 'is made tothe accompanying drawings which illustrate several FIG. 2 is across-sectional view taken along lines 2-2 of FIG.

FIG. 3 is a cross-sectional view, similar to that of FIG. 2 of a diaperof somewhat different internal construction;

FIGS. 4, 5, and 6 are each cross-sectional views, similar to that ofFIGS. 2 and 3, showing still further modifications of the absorbent;

FIG. 7 is a perspective view of a diaper with a different manner ofcontaining the absorbent;

FIG. 8 is a cross-sectional view taken along line 8-8 of FIG. 7; and

FIG. 9 is a cross-sectional view taken along line 9-9 of FIG. 7.

Referring to the drawings, in FIG. I is illustrated a diaper 10 having atop facing sheet 11. The facing sheet 11 may be formed of any of theconventional materials used as the facing in disposable diapers.Materials found to be particularly suitable are nonwoven fabrics resinbonded to give the desired wet and dry strength. The facing is readilypermeable to liquids so that the same can pass through into theunderlying absorbent 12.

A backing sheet 13 is provided, the backing l3 and the facing 11 beingsecured together around their edges giving a sealed border 14 extendingaround the periphery of the absorbent 12 which is contained between thefacing 11 and the backing I3. The absorbent 12 is formed of a sheet ofhydrophilic polyurethane foam having a thickness of about V4 inch. Thebacking 13, which acts primarily to support the absorbent 12 may be offabric either woven or nonwoven as long as it has sufficient tensilestrength and resistance to stretch when wet to support the absorbent 12after the same has become saturated. In the preferred practice thebacking is moisture impervious and formed of flexible water imperviousfilm such as polyethylene, either in free form or as a laminate to otherflexible sheet material such as paper or fabric.

By sealing the edges of the facing 11 and backing 13 together around theedges of the absorbent 12, the hydrophilic foam sheet comprising theabsorbent is contained within the diaper construction and prevented fromexpanding laterally beyond the edges of the facing 11 and backing 13when the absorbent 12 is wetted. If the hydrophilic foam sheetcomprising the absorbent 12 were not contained within the facing andbacking the expansion of the same would cause the hydrophilic foampolymer sheet to extend well beyond the edges of the absorbent pad 10.

Although the absorbent hydrophilic foam sheets have excellentwater-capacity and water-holding characteristics, it is found that thespreading of fluids therethrough in a vertical plane can besubstantially improved if there is placed in contact with the absorbentfoam sheet a sheet or sheets of creped cellulose wadding with thedirection of crepe running in the direction in which it might beanticipated a vertical lift of fluids would be desired. Thus, where theabsorbent pad of FIG. I is to be used for a diaper, it is desirable toinclude a sheet or sheets of cellulose crepe wadding in contact with thehydrophilic foam sheet with the direction of crepe running in thelongitudinal direction of the diaper. This aids in spreading the fluidlengthwise of the diaper particularly when the diaper is being worn andthe child is in an upright position.

In FIG. 3 is illustrated an absorbent pad in which the absorbent I2 isformed of a single sheet 15 of hydrophilic foam polymer and crepecellulose wadding 16. The creped cellulose wadding I6 is placed betweenthe facing sheet 11 and the hydrophilic foam polymer sheet 15. Exceptfor the diflerence in the manner of constructing the absorbent 12 theabsorbent pad of FIG. 3 is similar to that of FIG. 1.

If a plurality of crepe cellulose wadding sheets are employed and asingle sheet of polyurethane foam is used, it is preferred that thesheet of polyurethane foam be sandwiched between sheets of the crepecellulose wadding. Should, however, it be decided to use two or moresheets of the polyurethane foam, then the preferred practice is to placethe sheets of creped cellulose wadding with the creped cellulose waddingsheet between the hydrophilic foam sheets. Diapers having suchconstructions are illustrated in FIGS. 4 through 6. The diapersillustrated in FIGS. 4 through 6 have essentially the same generalconstruction as that of the diaper of FIG. I differing solely in themanner of constructing the absorbent I2. In FIG. 3, as previouslyindicated, one or more sheets of cellulose crepe tissue are placedbetween the facing 11 and the hydrophilic foam sheet 15 the crepe of thecellulose crepe tissue extending in the lengthwise direction of thediaper. In FIG. 4 the absorbent 12 of the diaper comprises a sheet ofhydrophilic foam I7 placed between two layers 18 and 19 of cellulosecrepe tissue with the crepe of tissue layer 18 running at right anglesto that of the direction of crepe in tissue layer 19. In FIG. 5 a stillfurther construction is illustrated in which cellulose crepe tissue 20is placed between two sheets 21 and 22 of hydrophilic foam polymer, thecrepe of the cellulose crepe tissue 20 running in the lengthwisedirection of the diaper.

In FIG. 6 the absorbent 12 of the diaper is composed of three sheets 23,24, and 25 of hydrophilic foam with cellulose crepe tissue 26 and 27placed therebetween.

The center hydrophilic foam sheet 24 is formed of a less resilient foampolymer than the two outer sheets 23 and 25, the two outer hydrophilicfoam polymer sheets giving to the diaper its softness and desirable feelwhile in the dry state. In the construction shown the center sheet 24 isformed of cellulose acetate foam which has excellent absorptionproperties and increases substantially in softness and resiliency whenwet. The outer sheets 23 and 25 are formed of soft, highly resilienthydrophilic polyurethane foam.

In FIGS. 7 through 9 is illustrated an absorbent pad 28 utilizing asomewhat different method of restraining the absorbent polymer foamsheet contained therein as the primary absorbent. Referring to FIGS. 7through 9 the facing 29 is longer than the absorbent 30 when theabsorbent is dry and the backing 31 is wider than the dry absorbent 30.The ends 32 and 33 of the facing 29 are wrapped around the ends ofbacking he absorbent 30 and secured to the absorbent 30 as bestillustrated in FIG. 9. Also, the extending edges 34 and 35 of thebacking 31 are wrapped around the sides of the absorbent 30 and securedto the facing 29 as best illustrated in FIG. 8. The absorbent 30 is thusrestrained within the facing 29 and backing 31 and prevented fromexpanding beyond the confines of the absorbent pad 28 when the same hasbecome wetted. The facing 29 and backing 31 are made of materialssimilar to those described for the absorbent pads of FIGS. 1 through 6.The absorbent 30 of pad 28 is formed of a sheet-36 of hydrophilicpolymer foam with crepe cellulose tissue 37 placed between the facing 29and polymer foam sheet 36.

With the polyurethane foam sheets being the primary absorbent as, forexample, in the constructions described, it is found that even thoughthe sheets of crepe cellulose wadding may tear or tend to shred, suchtearing of shredding is substantially reduced and any uncomfortablenesswith respect to the same is substantially eliminated due to thecushioning effect of the hydrophilic foam sheet.

Although certain embodiments have been used to describe the practice ofthe present invention, the invention is not to be limited to theseembodiments solely but is to be limited only as indicated by theappended claims.

Iclaim:

1. An absorbent pad comprising a flexible moisture permeable facing, aflexible backing and hydrophilic polymer foam sheet contained betweensaid facing and backing, said foam sheet being enclosed around its edgesto prevent lateral extension beyond the edges of said pad when wet, anda creped sheet of cellulosic fibers in contact with at least one surfaceof said hydrophilic polymer foam sheet.

2. An absorbent pad comprising a flexible moisture permeable facing, aflexible backing and hydrophilic polymer foam sheet contained betweensaid facing and said backing, said hydrophilic polymer foam sheet beingenclosed around its edges to prevent lateral extension beyond the edgesof said pad when wet, and a creped sheet of cellulosic fibers in contactwith at least one surface of said hydrophilic polymer foam with thedirection of crepe running in the lengthwise direction of said pad.

3. An absorbent pad comprising a flexible moisture permeable facing, aflexible backing and hydrophilic polymer foam sheet contained betweensaid facing and said backing, said hydrophilic polymer foam sheet beingenclosed around its edges to prevent lateral extension beyond the edgesof said pad when wet, and a creped sheet of cellulosic fibers in contactwith at least one surface of said hydrophilic polymer foam with thedirection of crepe running in the lengthwise direction of said pad,there being a crepe sheet of cellulosic fibers on the surface of saidhydrophilic polymer foam sheet nearest to said facing.

4. An absorbent pad comprising a flexible moisture permeable facing, aflexible backing and hydrophilic polymer foam sheet contained betweensaid facing and said backing, said hydrophilic polymer foam sheet beingenclosed around its edges to prevent lateral extension beyond the edgesof said pad when wet, and a creped sheet of cellulosic fibers in contactwith at least one surface of said hydrophilic polymer foam with thedirection of crepe running in the lengthwise direction of said pad,there being a crepe sheet of cellulosic fibers between the facing andsaid hydrophilic polymer foam sheet and between the backing and saidhydrophilic polymer foam sheet with the direction of crepe in said crepesheet adjacent said facing being substantially at right angles tothe'direction of crepe in said crepe sheet adjacent said backing,

5. An absorbent pad comprising a flexible moisture permeable facing, aflexible backing and hydrophilic polymer foam sheet contained betweensaid facing and said backing, said hydrophilic polymer foam sheet beingenclosed around its edges to prevent lateral extension beyond the edgesof said pad when wet, and a creped sheet of cellulosic fibers in contactwith at least one surface of said hydrophilic polymer foam with thedirection of crepe running in the lengthwise direction of said pad, saidcrepe sheet of cellulosic fibers being positioned between sheets of saidhydrophilic foam.

6; An absorbent pad comprising a flexible moisture permeable facing, aflexible backing and hydrophilic polymer foam sheet contained betweensaid facing and said backing, said hydrophilic polymer foam sheet beingenclosed around its edges to prevent lateral extension beyond the edgesof said pad when wet, said hydrophilic foam sheet being formed of aplurality of sheets of hydrophilic polymer foam, at least one of saidsheets of hydrophilic polymer foam having a softness in the dry stateless than the softness of said other hydrophilic polymer foam.

7. An absorbent pad comprising a flexible moisture permeable facing, aflexible backing and hydrophilic polymer foam sheet contained betweensaid facing and said backing, said hydrophilic polymer foam sheet beingenclosed around its edges to prevent lateral extension beyond the edgesof said pad when wet, said hydrophilic foam sheet being formed of aplurality of sheets of hydrophilic polymer foam, at least one of saidsheets of hydrophilic polymer foam having a softness in the dry stateless than the softness of said other hydrophilic polymer foam, saidsheet of hydrophilic polymer foam of lesser softness being positionedbetween sheets of hydrophilic polymer foam of greater softness.

8. An absorbent pad comprising a flexible moisture permeable facing, aflexible backing and hydrophilic polymer foam sheet contained betweensaid facing and said backing, said hydrophilic polymer foam sheet beingenclosed around its edges to prevent lateral extension beyond the edgesof said pad when wet, and a sheet of cellulosic fibers in contact withat least one surface of said hydrophilic polymer foam.

2. An absorbent pad comprising a flexible moisture permeable facing, aflexible backing and hydrophilic polymer foam sheet contained betweensaid facing and said backing, said hydrophilic polymer foam sheet beingenclosed around its edges to prevent lateral extension beyond the edgesof said pad when wet, and a creped sheet of cellulosic fibers in contactwith at least one surface of said hydrophilic polymer foam with thedirection of crepe running in the lengthwise direction of said pad. 3.An absorbent pad comprising a flexible moisture permeable facing, aflexible backing and hydrophilic polymer foam sheet contained betweensaid facing and said backing, said hydrophilic polymer foam sheet beingenclosed around its edges to prevent lateral extension beyond the edgesof said pad when wet, and a creped sheet of cellulosic fibers in contactwith at least one surface of said hydrophilic polymer foam with thedirection of crepe running in the lengthwise direction of said pad,there being a crepe sheet of cellulosic fibers on the surface of saidhydrophilic polymer foam sheet nearest to said facing.
 4. An absorbentpad comprising a flexible moisture permeable facing, a flexible backingand hydrophilic polymer foam sheet contained between said facing andsaid backing, said hydrophilic polymer foam sheet being enclosed aroundits edges to prevent lateral extension beyond the edges of said pad whenwet, and a creped sheet of cellulosic fibers in contact with at leastone surface of said hydrophilic polymer foam with the direction of creperunning in the lengthwise direction of said pad, there being a crepesheet of cellulosic fibers between the facing and said hydrophilicpolymer foam sheet and between the backing and said hydrophilic polymerfoam sheet with the direction of crepe in said crepe sheet adjacent saidfacing being substantially at right angles to the direction of crepe insaid crepe sheet adjacent said backing.
 5. An absorbent pad comprising aflexible moisture permeable facing, a flexible backing and hydrophilicpolymer foam sheet contained between said facing and said backing, saidhydrophilic polymer foam sheet being enclosed around its edges toprevent lateral extension beyond the edges of said pad when wet, and acreped sheet of cellulosic fibers in contact with at least one surfaceof said hydrophilic polymer foam with the direction of crepe running inthe lengthwise direction of said pad, said crepe sheet of cellulosicfibers being positioned between sheets of said hydrophilic foam.
 6. Anabsorbent pad comprising a flexible moisture permeable facing, aflexible backing and hydrophilic polymer foam sheet contained betweensaid facing and said backing, said hydrophilic polymer foam sheet beingenclosed around its edges to prevent lateral extension beyond the edgesof said pad when wet, said hydrophilic foam sheet being formed of aplurality of sheets of hydrophilic polymer foam, at least one of saidsheets of hydrophilic polymer foam having a softness in the dry stateless than the softness of said other hydrophilic polymer foam.
 7. Anabsorbent pad comprising a flexible moisture permeable facing, aflexible backing and hydrophilic polymer foam sheet contained betweensaid facing and said backing, said hydrophilic polymer foam sheet beingenclosed around its edges to prevent lateral extension beyond the edgesof said pad When wet, said hydrophilic foam sheet being formed of aplurality of sheets of hydrophilic polymer foam, at least one of saidsheets of hydrophilic polymer foam having a softness in the dry stateless than the softness of said other hydrophilic polymer foam, saidsheet of hydrophilic polymer foam of lesser softness being positionedbetween sheets of hydrophilic polymer foam of greater softness.
 8. Anabsorbent pad comprising a flexible moisture permeable facing, aflexible backing and hydrophilic polymer foam sheet contained betweensaid facing and said backing, said hydrophilic polymer foam sheet beingenclosed around its edges to prevent lateral extension beyond the edgesof said pad when wet, and a sheet of cellulosic fibers in contact withat least one surface of said hydrophilic polymer foam.